Submitted to: Research Workers in Animal Diseases Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 10/1/2004
Publication Date: 11/1/2004
Citation: Durso, L.M., Bono, J.L., Keen, J.E. 2004. Multiplex PCR for serotyping Escherichia coli O26:H11 [abstract]. Research Workers in Animal Diseases Conference. p. 121.
Technical Abstract: The most commonly isolated non-O157:H7 shiga-toxigenic Escherichia coli serotype is O26:H11. It is associated with human clinical disease worldwide, and has been isolated exclusively from humans, cattle, and cattle products. Serotyping of E. coli somatic (O) and flagellar (H) antigens is essential for accurate diagnostics and surveillance of pathogenic strains. Conventional serotyping is the gold standard for E. coli identification, but it involves costly reagents and highly trained personnel, thus limiting its use to reference laboratories. We developed a multiplex PCR serotyping protocol for E. coli O26:H11 that targets, genetically, the same somatic and flagellar antigens used in conventional serotyping, and that can be easily performed in most laboratories. Primers were designed based on sequencing of O and H antigen genes from multiple E. coli O26 and H11 strains. The O26 PCR had a sensitivity of 0.98 (84/85 O26 isolates matching conventional serotyping) and a specificity of 1.00 (240 E. coli isolates representing 111 O serogroups). The H11 PCR had a sensitivity of 0.94 (35/37 H11 isolates matching conventional serotyping) and a specificity of 1.00 (137 E. coli isolates representing 51 H serogroups). In a blind panel, the molecular and conventional serotyping results agreed for 39/42 strains tested. A limitation of our PCR assay is that, unlike conventional serotyping, it does not provide phenotypic (gene expression) information. However, the genetic information this assay provided permitted typing of phenotypically silent strains, such as rough LPS O26 strains and non-motile H11 isolates. Thus, molecular serotyping can enable acquisition of relevant clinical or epidemiological data on strains that were untypeable by conventional serotyping.